1. Field of Invention
This invention relates generally to fluid control systems and more particularly to time-based control of fluid volume as it relates to integration with and optimization of fluid-utilizing systems into which this invention is interfaced.
2. Description of Prior Art
Prior to implementation of the existing Kruto method and apparatus, U.S. Pat. No. 4,425,930, fluid flow control was typically accomplished using a simple sense-and-switching means to control a single, normally-closed solenoid valve. One example is the utilization of a thermostatic switch electrically connected to a solenoid valve for gas furnace supply line cycling. Low ambient temperature -signifying a demand for heat- causes the switch to close. Closing of the switch causes the valve to open, thereby supplying the furnace with a single or "maximum", continuous gas flow volume. Gas flow continues until a sufficient supply of heat raises the ambient temperature, causing the switch to open and therefore, the valve to close. Successive demands for heat cause this cycle to be repeated. Other existing supply line as well as numerous other fluid flow control applications were implemented utilizing essentially the same basic apparatus.
Again utilizing gas furnace applications for illustrative purposes, in relevant part, the prior Kruto patent observed that introducing a period of reduced gas flow volume reduces overall fuel consumption without significant impact on warming. Thus, a second, normally-closed, solenoid valve means was added to the supply line to provide three independently selectable fluid flow volumes: no flow (both closed); maximum flow (both open); and minimum flow (only the existing valve is open). Two thermostatically and sequentially triggered, valve-specific timers were also added for simple, automatically scheduled fluid volume switching within the conventional thermostatic cycle. Closing of the thermostatic switch thus results in a first interval of maximum fluid flow volume, a second interval of minimum fluid flow volume and--should the switch remain closed indicating continued demand--a third interval of maximum fluid flow volume. Again, the same basic apparatus with minimal, rather obvious modification is equally applicable to numerous other control applications.
While the Kruto apparatus produces positive results, as with many early attempts to implement a generalized concept based upon preliminary findings, numerous practicalities were overlooked. For example, the apparatus is not a functionally independent module. User control and interfacing is limited to manual presets for the two discrete timers, powered uninterrupted maximum flow or "apparatus bypass" and conventional sense/switching means manipulation--in this illustration, thermostatic switch (overall cycle length) adjustment. No means for immediate feedback is provided, including for adjustments made. These oversights present a number of key disadvantages.
One disadvantage of the prior Kruto apparatus is its difficult installation. Extensive technician support is needed for connection to the existing sense-switching means, replacement of the existing valve system and both initial and repeated manual adjustment for system-specific optimization. While this is especially true of retrofit applications, new manufacture also suffers due to the variety of system configurations and time-varying, user-specific requirements.
A second disadvantage of the prior Kruto apparatus is the lack of an effective feedback means for alerting even a technician as to proper adjustment for maximum efficiency. Thus optimal efficiency, particularly for non-standard systems, can only be determined by review of fuel consumption statistics and host-system effectiveness over an extended period of time.
A third disadvantage of the prior Kruto apparatus is that fluid flow volume is not optimizeable either individually or in conjunction with timer variation to provide an optimal fluid flow efficiency versus host-system effectiveness compromise. While the "optimal" minimum-to-maximum fluid flow volume ratio can vary based upon the initial system configuration and various modifications, the "actual" ratio is chosen during manufacture based upon the specific valves chosen. The utilization of two discrete valves further erroneously assumes a two or three period optimal schedule.
Compounding these disadvantages is the control means itself. Essentially blind manual manipulation in proximity to, for example a furnace, combined with a complex, wait-and-see type statistical and useability analysis, unavailability of analytical equipment and related expense realistically preempts achieving optimal or even near-optimal system performance.
A fourth disadvantage of the prior Kruto apparatus is that discrete timers and normally closed, two-state valve means are necessarily utilized. The discrete timers are inherently prone to inaccuracies. Given the lack of immediate feedback and correction means, these inaccuracies may well go unnoticed despite a decrease in overall system performance. In addition, the normally closed valve means require power in order to eliminate apparatus interference with the overall system. Thus diagnosis and even safety may well be compromised in the event of a system and/or apparatus failure.
A fifth disadvantage of the prior Kruto apparatus is that no means is provided for remote monitoring, analysis, control and other automation-enabling capabilities, many of which are discussed in more detail below.